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<tr class="t-nv-h2"><td colspan="5"> std::future extensions</td></tr>
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</table></div><div></div></div></div></div><div class="t-navbar-sep"> </div></div>
<p>The C++ Extensions for Concurrency, ISO/IEC TS 19571:2016, defines the following new components for the C++ standard library:
</p>
<h3><span class="mw-headline" id="Continuations_and_other_extensions_for_std::future">Continuations and other extensions for std::future</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code><a href="https://en.cppreference.com/mwiki/index.php?title=cpp/header/experimental/future&amp;action=edit&amp;redlink=1" class="new" title="cpp/header/experimental/future (page does not exist)">&lt;experimental/future&gt;</a></code> </div>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="future.html" title="cpp/experimental/future"> <span class="t-lines"><span>future</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   A version of <span class="t-lc"><a href="../thread/future.html" title="cpp/thread/future">std::future</a></span> enhanced with continuations and other features  <br> <span class="t-mark">(class template)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="shared_future.html" title="cpp/experimental/shared future"> <span class="t-lines"><span>shared_future</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   A version of <span class="t-lc"><a href="../thread/shared_future.html" title="cpp/thread/shared future">std::shared_future</a></span> enhanced with continuations and other features  <br> <span class="t-mark">(class template)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="concurrency/promise.html" title="cpp/experimental/concurrency/promise"> <span class="t-lines"><span>promise</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   a modified version of <span class="t-lc"><a href="../thread/promise.html" title="cpp/thread/promise">std::promise</a></span>  that uses <span class="t-lc">std::experimental::future</span>  <br> <span class="t-mark">(class template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="concurrency/packaged_task.html" title="cpp/experimental/concurrency/packaged task"> <span class="t-lines"><span>packaged_task</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   a modified version of <span class="t-lc"><a href="../thread/packaged_task.html" title="cpp/thread/packaged task">std::packaged_task</a></span> that uses <span class="t-lc">std::experimental::future</span>  <br> <span class="t-mark">(class template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="when_all.html" title="cpp/experimental/when all"> <span class="t-lines"><span>when_all</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   produces a future that becomes ready when all given futures or shared_futures are ready  <br> <span class="t-mark">(function template)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="when_any.html" title="cpp/experimental/when any"> <span class="t-lines"><span>when_any</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   produces a future that becomes ready when at least one of the given futures or shared_futures is ready  <br> <span class="t-mark">(function template)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="make_ready_future.html" title="cpp/experimental/make ready future"> <span class="t-lines"><span>make_ready_future</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   produces a future that is ready immediately and holds the given value  <br> <span class="t-mark">(function template)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="make_exceptional_future.html" title="cpp/experimental/make exceptional future"> <span class="t-lines"><span>make_exceptional_future</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   produces a future that is ready immediately and holds the given exception  <br> <span class="t-mark">(function template)</span> </td></tr>
</table>
<h3><span class="mw-headline" id="Feature_test_macros">Feature test macros</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code><a href="https://en.cppreference.com/mwiki/index.php?title=cpp/header/experimental/future&amp;action=edit&amp;redlink=1" class="new" title="cpp/header/experimental/future (page does not exist)">&lt;experimental/future&gt;</a></code> </div>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>__cpp_lib_experimental_future_continuations</span></span></div></div>
</td>
<td>   a value of at least <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">201505</span></span></span> indicates that future::then and other extensions are supported  <br> <span class="t-mark">(macro constant)</span>
</td></tr>


<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code><a href="https://en.cppreference.com/mwiki/index.php?title=cpp/header/experimental/latch&amp;action=edit&amp;redlink=1" class="new" title="cpp/header/experimental/latch (page does not exist)">&lt;experimental/latch&gt;</a></code> </div>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>__cpp_lib_experimental_latch</span></span></div></div>
</td>
<td>   a value of at least <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">201505</span></span></span> indicates that the latch type is supported  <br> <span class="t-mark">(macro constant)</span>
</td></tr>


<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code><a href="https://en.cppreference.com/mwiki/index.php?title=cpp/header/experimental/barrier&amp;action=edit&amp;redlink=1" class="new" title="cpp/header/experimental/barrier (page does not exist)">&lt;experimental/barrier&gt;</a></code> </div>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>__cpp_lib_experimental_barrier</span></span></div></div>
</td>
<td>   a value of at least <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">201505</span></span></span> indicates that barrier type is supported  <br> <span class="t-mark">(macro constant)</span>
</td></tr>


<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code><a href="https://en.cppreference.com/mwiki/index.php?title=cpp/header/experimental/atomic&amp;action=edit&amp;redlink=1" class="new" title="cpp/header/experimental/atomic (page does not exist)">&lt;experimental/atomic&gt;</a></code> </div>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>__cpp_lib_experimental_atomic_smart_pointers</span></span></div></div>
</td>
<td>   a value of at least <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">201505</span></span></span> indicates that the atomic smart pointers are supported  <br> <span class="t-mark">(macro constant)</span>
</td></tr>

</table>
<h2><span class="mw-headline" id="Merged_into_C.2B.2B20"> Merged into C++20 </span></h2>
<p>The following components of the Concurrency TS have been adopted into the C++20 standard.
</p>
<h3><span class="mw-headline" id="Latches_and_barriers">Latches and barriers</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code><a href="https://en.cppreference.com/mwiki/index.php?title=cpp/header/experimental/latch&amp;action=edit&amp;redlink=1" class="new" title="cpp/header/experimental/latch (page does not exist)">&lt;experimental/latch&gt;</a></code> </div>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="latch.html" title="cpp/experimental/latch"> <span class="t-lines"><span>latch</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   single-use thread barrier  <br> <span class="t-mark">(class)</span> </td></tr>

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code><a href="https://en.cppreference.com/mwiki/index.php?title=cpp/header/experimental/barrier&amp;action=edit&amp;redlink=1" class="new" title="cpp/header/experimental/barrier (page does not exist)">&lt;experimental/barrier&gt;</a></code> </div>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="barrier.html" title="cpp/experimental/barrier"> <span class="t-lines"><span>barrier</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   reusable thread barrier  <br> <span class="t-mark">(class)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="flex_barrier.html" title="cpp/experimental/flex barrier"> <span class="t-lines"><span>flex_barrier</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   reusable thread barrier with customizable behavior on completion  <br> <span class="t-mark">(class)</span> </td></tr>
</table>
<h3><span class="mw-headline" id="Atomic_smart_pointers">Atomic smart pointers</span></h3>
<p>These class templates replace the shared_ptr <a href="../memory/shared_ptr/atomic.html" title="cpp/memory/shared ptr/atomic">atomic function overloads</a>
</p>
<table class="t-dsc-begin">

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code><a href="https://en.cppreference.com/mwiki/index.php?title=cpp/header/experimental/atomic&amp;action=edit&amp;redlink=1" class="new" title="cpp/header/experimental/atomic (page does not exist)">&lt;experimental/atomic&gt;</a></code> </div>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="atomic_shared_ptr.html" title="cpp/experimental/atomic shared ptr"> <span class="t-lines"><span>atomic_shared_ptr</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   atomic version of std::shared_ptr  <br> <span class="t-mark">(class template)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="atomic_weak_ptr.html" title="cpp/experimental/atomic weak ptr"> <span class="t-lines"><span>atomic_weak_ptr</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-concurrency-ts t-mark-ts">(concurrency TS)</span></span></span></div></div>
</td>
<td>   atomic version of std::weak_ptr  <br> <span class="t-mark">(class template)</span> </td></tr>
</table>

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